This invention relates to a control apparatus for vehicles which has steering clutches and steering brakes, and more particularly to a control apparatus which is adapted to disengage a speed change gear clutch in response to the running, stopping and braking of vehicles.
Conventional control apparatus of this type have a pair of steering control members (pedals or levers) which are coupled with a pair of steering clutches and a pair of steering brakes via a linkage. When a selected one of steering control members is actuated, the steering clutch for the actuated member is disengaged during which time one of the running devices of the vehicle is in free condition, and thereafter when the selected member is further operated, the steering brake is applied during which time the running device in the free condition is braked so as to be able to turn the vehicle slowly or rapidly. Therefore, when the pair of steering control members are actuated, both of the steering clutches are disengaged and, subsequently, both of the steering brakes are operated to stop the vehicle. If the vehicle is stopped on a sloped ground, it ascends the ground a moment since the running device is first in the free condition and then braked.
In addition, when the vehicle that is braked on the sloped ground during which time both of the steering clutches are disengaged and both of the steering brakes are applied is to be turned or started forwardly or rearwardly by releasing one of the steering control members which are both actuated, the steering clutch for the released member is engaged only after the steering brake for the released member is released when one of the running devices is in the free condition. Thus, this has led to a drawback in that the vehicle is subjected to a dangerous, unexpected turn until the running device in the free condition is driven.
A control apparatus as disclosed in U.S. Pat. No. 3,494,449 has been developed to eliminate the above-noted difficulties. Such a control apparatus is so arranged that when a selected one of a pair of steering control members is actuated, the steering clutch for the actuated member is disengaged, and as the selected member is further actuated, the steering brake therefor is applied so as to be able to control the slow or rapid turn of the vehicle. Thus, the driving power to the running devices is not interrupted during the running, stopping and braking of the vehicle, so that the running devices are prevented from becoming free and the vehicle is prevented from ascending for a moment or turning unexpectedly on a sloped ground. However, the difficlty with such an arrangement is that there is required a very large amount of braking force until the torque converter is stalled or the engine is stopped because a brake is applied without interrupting the driving force to the running devices, thus normally requiring an additional procedure to disengage the main clutch for a power transmission device or to slip a speed change gear into neutral. Therefore, this prior art attempt necessitates a complicated control operation.